Centrifugal electric pump for suction of aeriform fluids

ABSTRACT

A centrifugal electric pump ( 1 ) for suction of aeriform fluids includes:
         an electric motor ( 2 ) provided with a rotating shaft ( 3 );   a suction body ( 4 ) provided with an intake ( 5 ) for the aeriform fluid and with at least one exhaust port ( 6 );   at least one fan ( 8 ), fitted onto the shaft ( 3 ) and driven in movement by the motor ( 2 ), adapted to draw in a flow of air from the intake ( 5 ), spin it and discharge it outside the suction body ( 4 ) through the at least one exhaust port ( 6 ),
 
wherein the electric motor ( 2 ) includes:
   a rotor with windings ( 9 );   a stator ( 10 ) adapted to create a magnetic field inside which the rotor ( 9 ) rotates,
 
and wherein the stator ( 10 ) is of the type with permanent magnets and the rotor ( 9 ) rotates at a high number of revolutions.

The present invention relates to the field of fluid working machines.

In particular, the present invention concerns a centrifugal electric pump for suction of aeriform fluids, particularly suitable for use as a vacuum pump in vacuum cleaning and floor washing machines, for cleaning surfaces through the suction of air containing dust or liquids, used both in a domestic as well as in an industrial and professional environment.

These electric pumps are commercially defined as “turbines”, due to their very high rotation speed, notwithstanding the fact that they are working machines. In fact, the number of revolutions greatly exceeds 3,000 per minute, reaching 7,000-8,000 and over.

Centrifugal electric pumps for suction of aeriform fluids of conventional type essentially comprise an electric motor with a high number of revolutions and a suction pump body provided with an intake for suction of the fluid and with at least one exhaust port for discharge of the same fluid belonging to the same pump body. The movement of the fluid in the inner chamber inside said suction body is caused by at least one impeller, or fan, contained therein.

In simpler and inexpensive vacuum cleaners, through-flow motors are generally used, in which, after being filtered, the hot air laden with fine dust is blown through the motor to be cooled.

In vacuum cleaners that also function as wet vacuum cleaners and floor washing machines it is necessary to use motors with “by-pass” technology, in which the body of the suction pumps is completely separated from that of the motor. In this latter case, there is no contact between the air laden with dust sucked in, or between any liquid used for washing, and the electric motor. This electric motor, which can be supplied either with direct current or with alternating current, is essentially formed by a stator, the outermost and fixed part, and by a rotor, rotating therein.

The stator is adapted to generate a magnetic field and, in applications on turbines and electric pumps, it is generally made with copper windings through which the electric current flows.

In particular, a conventional stator is formed by laminations made of silicon steel alloy or in solid steel, structured to define slots, around which the coils of the copper windings are wound. The laminated core is insulated from said coils by means of special insulating paper that covers the slots.

Also the rotor is generally of the type with windings, formed by a ferromagnetic cylinder shaped so as to have a series of axially arranged slots, positioned inside which are the windings, or coils, that define the armature circuit. Said windings are connected to one another by means of a device called commutator or slip-ring (or Pacinotti ring).

Said commutator also acts as a rotary switch with sliding contacts, and is adapted to switch the electric current between the coils, thereby varying the interaction with the magnetic field generated by the stator.

During rotation of the rotor, said windings come into contact with the brushes, through which electric current is supplied to the motor and the torque generated by rotation is proportional to the current that flows through the windings of the rotor.

These electric motors, to be used on centrifugal electric pumps and turbines that require a high power and a high number of revolutions of the rotor, are complex to build, require a lot of labor and are consequently very costly.

Moreover, these types of electric motors are designed ad hoc on the basis of the requirements of the machine on which they are installed: each model is custom designed and manufactured, defining the precise number of slots and coils and coordinating the number of turns of the rotor and of the stator accordingly.

The object of the invention is to overcome these limits, producing a centrifugal electric pump for suction of aeriform fluids provided with an electric motor of by-pass type with a high number of revolutions, which is highly efficient and at the same time can be produced easily, rapidly and inexpensively.

A further object of the invention is to produce an electric pump provided with an electric motor with easily variable power, so as to ensure an electric pump with a wide range of performances.

These objects are achieved with a centrifugal electric pump for suction of aeriform fluids comprising:

-   -   an electric motor of by-pass type provided with a rotating         shaft;     -   a suction body provided with an intake for the aeriform fluid         and at least one exhaust port belonging to the same suction         body;     -   at least one fan, fitted onto said shaft and driven in movement         by said motor, adapted to draw in a flow of air through said         intake, spin it and discharge it outside said suction body         through said at least one exhaust port,         wherein said electric motor comprises:     -   a rotor with windings;     -   a stator adapted to create a magnetic field inside which said         rotor rotates, characterized in that said stator is of the type         with permanent magnets and said rotor rotates at a high number         of revolutions.

In particular, said rotor rotates at a number of revolutions higher than 7,000-8,000 rpm.

According to a first embodiment of the invention, said stator comprises a hollow cylindrical body made of iron, provided on the inside with two permanent magnets with opposite polarity, adapted to generate a magnetic field inside said hollow cylindrical body.

Advantageously, said permanent magnets are substantially semi-cylindrical in shape, and said stator comprises leaf springs, provided inside said hollow cylindrical body, adapted to block said permanent magnets in position.

According to a further embodiment of the invention, said rotor with windings comprises a plurality of coils connectable to one another in parallel or in series.

In a particularly preferred embodiment of the invention, said stator comprises a third permanent magnet, arranged outside said hollow cylindrical body, whose magnetic field is adapted to interact with the magnetic field generated by the two internal magnets, so as to vary the number of revolutions of said rotor.

In particular, the position taken by said third magnet on the outer surface of said hollow cylindrical body, with respect to the arrangement of the two internal magnets, is adapted to modify the magnetic field generated by the stator and therefore its interaction with the magnetic field generated by the rotor, determining a higher or lower rotation speed.

Advantageously, said electric motor comprises means for adjusting the position of said third magnet around the outer surface of said hollow cylindrical body.

In an even more preferable embodiment of the invention, said adjustment means are accessible from the outside of said motor.

The advantages of the invention are as follows.

The main advantage consists in the simple construction and compact size of the motor, and in particular of the stator of the electric pump: numerous components, to be designed, produced and assembled, and copper wire windings are no longer required; the stator is formed simply by placing two magnets with opposite polarity inside a hollow cylindrical body, into which the rotor will also then be placed freely.

This simple construction also translates into a considerable saving in costs for the manufacturer of electric pumps and facilitates cooling of the motor using a specific fan, as is customary on these types of by-pass motors.

The electric motor with stator with permanent magnets fitted to the electric pump according to the invention is able to satisfy a wide range of power requirements, due to the flexibility offered by the presence of the third magnet, without the need to make substantial changes to ensure the high number of revolutions required by specific applications.

These and other advantages will be more apparent below in the description of a preferred embodiment of the invention, provided by way of non-limiting example, and with the aid of the figures, wherein:

FIG. 1 represents a cross sectional view of a centrifugal electric pump for suction of aeriform fluids according to the invention;

FIGS. 2-4 represent, respectively in an overall axonometric view, in a axonometric view in longitudinal section and in a top view, an electric motor with permanent magnets for centrifugal electric pumps according to the invention;

FIGS. 5 and 6 represent, respectively in an overall axonometric view and in an axonometric view in longitudinal section, the stator of the motor of FIG. 2;

FIG. 7 represents, in an axonometric view, an electric motor with permanent magnets according to a possible embodiment of the invention;

FIG. 8 represents, in a top view, the stator of FIG. 7 with reference to the intensity of the magnetic field generated.

With reference to FIG. 1, this shows a centrifugal electric pump 1 for suction of aeriform fluids provided with an electric motor 2 of by-pass type with permanent magnets according to a preferred embodiment of the invention.

Said electric pump 1 is essentially formed by an electric motor 2 provided with a drive shaft 3, a suction body 4 and one or more fans 8 adapted to move a flow of air.

In the embodiment shown, said suction body 4 is cylindrical in shape and comprises a circular base provided with a suction intake 5 placed in the center and a lateral surface provided with a plurality of exhaust ports 6, adapted to drain off the flow of air drawn in, without passing through said motor 2.

Said body 4 is in fact closed at the top by a cover 7 adapted also to act as a base for said motor 2.

Said fans 8 are fitted onto said drive shaft 3 and are driven in movement by said motor 2.

With particular reference to FIGS. 2-4, these show the detail of the electric motor 2 with permanent magnets fitted to the electric pump 1 of Fig. according to the invention.

Said electric motor 2 essentially comprises:

-   -   a rotor with windings 9, adapted to operate at a high number of         revolutions, at least 7,000-8,000 rpm;     -   a stator 10, of the type with permanent magnets, adapted to         create a magnetic field inside which said rotor 9 rotates.

An air gap of a few tenths of a millimeter is present between the stator 10 and rotor 9, to allow the rotor 9 to rotate freely.

The rotor 9 is formed by a laminated core 16 substantially in the shape of an annulus, with an inner hole for the drive shaft 3 to pass through, and outer grooves 17, called rotor slots, for accommodating the rotor winding.

In the embodiment shown, where the motor 2 can reach speeds of up to 15,300 rpm with the suction intake of the pump open and 18,000 rpm with the suction intake of the pump closed, the rotor winding is formed by twenty-four copper induction coils 14.

The increased current absorption, caused by replacement of the conventional stator with a stator 9 with permanent magnets, is advantageously compensated by modifying the number of turns for each coil 14 inside the rotor 9.

For example, in the case described above, each coil 14 comprises six turns.

With particular reference to FIGS. 5 and 6, these show the stator 10 with permanent magnets included in the electric motor 2 of the electric pump 1 according to the invention.

Said stator 10 comprises a hollow cylindrical body 11 made of iron, provided on the inside with two permanent magnets 12 a and 12 b, with opposite polarity, adapted to generate a magnetic field inside said hollow cylindrical body 11.

Said permanent magnets 12 a and 12 b are substantially semi-cylindrical in shape and are supported and pressed against the inner wall of said hollow cylindrical body 11 by leaf springs 13 fixed to the wall of the same body.

To be able to advantageously vary the magnetic field generated by the stator 10, and consequently the number of revolutions and the power of the motor 2, a third permanent magnet 15 can be provided on said stator 10, as shown in FIGS. 7 and 8.

Said third magnet 15 is arranged outside said hollow cylindrical body 11, but its magnetic field is adapted to interact with the magnetic field generated by the two magnets 12 a and 12 b inside the cylindrical body 11, so as to vary the number of revolutions of said rotor 9.

In particular, the position taken by said third magnet 15 on the outer surface of said hollow cylindrical body 11, with respect to the arrangement and the polarity of the two internal magnets 12 a and 12 b, modifies interaction between the magnetic field generated by said third magnet 15 and the magnetic field inside said cylindrical body 11.

For example, as it can be seen in the schematic section of FIG. 8, if the third magnet 15 is arranged outside the hollow cylindrical body 11 so that its face with negative polarity faces the face of the internal magnet 12 b with positive polarity, the total magnetic field of the stator 10 will increase in intensity. Vice versa, if the negative face of the third magnet 15 is arranged outside the hollow cylindrical body 11 facing the negative face of the internal magnet 12 a, the total magnetic field of the stator 10 will decrease in intensity.

The position of said third magnet 15 on the outer surface of the cylindrical body 11 is therefore fundamental, and advantageously can be easily adjusted and varied according to the needs and to the power requirement of the electric motor 2.

In this regard, in a possible embodiment of the invention (not shown), said electric motor 2 can comprise specific adjustment means, accessible from the outside of the motor 2, arranged to vary the position of said third magnet 15 around the surface of said cylindrical body 11, thereby allowing modulation of the rotation speed of the rotor 9 and the power of the motor 2 without requiring to take action with the replacement of components.

Operation of the electric motor 2 according to the invention inside a centrifugal electric pump 1 is described below.

The electric current passes through a winding 14 of turns located in the rotor 9. This winding, composed of copper wires, creates an electromagnetic field.

The electromagnetic field thus created is immersed in another magnetic field, the one created by the stator 10, which is characterized by the presence of two polar pairs, the permanent magnets 12 a and 12 b.

Through electromagnetic induction the rotor 9 starts to rotate, as the magnetic field of the rotor 9 tends to align itself with that of the stator 10.

During rotation, the sliding contact switch switches the electric current between the coils 14 of the rotor 9, so that the magnetic field of the stator 10 and that of the rotor 9 never become perfectly aligned, thereby obtaining continuous rotation.

In the embodiment illustrated in FIGS. 7 and 8 it is possible to modify, continuously and at the user's discretion, the position of the third magnet 15 so as to easily adjust the rotation speed of the rotor 9.

Naturally, a person with average skill in the art can vary the number of permanent magnets of the stator, the number of the slots and of the coils of the rotor and the number of the turns of each coil, and can also use the motor to operate other types of fluid working machines, also multistage, without departing from the scope of the present invention. 

1. A centrifugal electric pump (1) for suction of aeriform fluids comprising: an electric motor (2) of by-pass type provided with a rotating shaft (3); a suction body (4) provided with an intake (5) for the aeriform fluid and with at least one exhaust port (6) belonging to the same suction body (4); at least one fan (8), fitted onto said shaft (3) and driven in movement by said motor (2), adapted to draw in a flow of air from said intake (5), spin it and discharge it outside said suction body (4) through said at least one exhaust port (6), wherein said electric motor (2) comprises: a rotor with windings (9); a stator (10) adapted to create a magnetic field inside which said rotor (9) rotates, characterized in that said stator (10) is of the type with permanent magnets and said rotor (9) rotates at a high number of revolutions. 2) The centrifugal electric pump (1) according to claim 1, characterized in that said rotor (9) rotates at a number of revolutions higher than 7,000-8,000 rpm. 3) The centrifugal electric pump (1) according to claim 1, characterized in that said stator (10) comprises a hollow cylindrical body (11) made of iron, provided on the inside with two permanent magnets (12 a, 12 b) with opposite polarity, adapted to generate a magnetic field inside said hollow cylindrical body (11). 4) The centrifugal electric pump (1) according to claim 3, characterized in that said permanent magnets (12 a, 12 b) are substantially semi-cylindrical in shape. 5) The centrifugal electric pump (1) according to claim 4, characterized in that said stator (10) comprises leaf springs (13), provided inside said hollow cylindrical body (11), adapted to block said permanent magnets (12 a, 12 b) in position. 6) The centrifugal electric pump (1) according to claim 1, characterized in that said rotor (9) with windings comprises a plurality of coils (14) connectable to one another in parallel or in series. 7) The centrifugal electric pump (1) according to claim 1, characterized in that said stator (10) comprises a third permanent magnet (15), arranged outside said hollow cylindrical body (11), whose magnetic field is adapted to interact with the magnetic field generated by two internal magnets (12 a, 12 b), so as to vary the number of revolutions of said rotor (9). 8) The centrifugal electric pump (1) according to claim 7, characterized in that the position taken by said third magnet (15) on the outer surface of said hollow cylindrical body (11), with respect to the arrangement of the two internal magnets (12 a, 12 b), is adapted to modify the magnetic field generated by the stator (10) and therefore its interaction with the magnetic field generated by the rotor (9), determining a higher or lower rotation speed. 9) The centrifugal electric pump (1) according to claim 8, characterized in that said electric motor (2) comprises means for adjusting the position of said third magnet (15) around the outer surface of said hollow cylindrical body (11). 10) The centrifugal electric pump (1) according to claim 9, characterized in that said adjustment means are accessible from the outside of said motor (2). 